Anemia is a reduction in the normal levels of erythrocytes per cubic millimeter, the quantity of hemoglobin, or in the volume of packed red cells per one hundred milliliters. Although anemia is not a specific disease, it is the principal manifestation of a number of abnormal conditions such as deficiency conditions (caused by lack of iron, vitamin B12, or folic acid), hereditary disorders of the erythrocyte, disorders of the hematopoietic tissues (bone marrow damage or a hyperactive spleen) and gastrointestinal tract bleeding as a result of cancer or hemorrhage associated with organ trauma. As such, the diagnosis of the etiology of a patient's anemia is of great importance in enabling a treating physician to choose an appropriate therapeutic regimen.
Hemolysis is the disruption of the erythrocyte membrane causing release of hemoglobin and is one of the main causes of anemia. Hemolysis can occur as a result of a variety of factors, e.g. intracorpuscular hereditary defects within the erythrocyte triggered by extracellular factors such as drugs, plasma components, or splenic hyperactivity; or extracorpuscular factors such as infection, immunologic disease, and chemical or physical agents.
Anemia due to hemolysis is currently diagnosed by examination of a number of indirect markers. Findings of reticulocytosis (due to the increased efforts of the bone marrow to compensate for excessive erythrocyte destruction), increased erythrocyte fragility, shortened erythrocyte life span, hyperbilirubinemia, elevated serum levels of lactate dehydrogenase, increased fecal and urinary urobilinogen, or hemoglobinemia in cases of massive intravascular hemolysis, for example, will result in a diagnosis of hemolysis. However, use of such indirect indicators in the diagnosis of hemolysis is inaccurate. Very often, in patients who are suspected of suffering from hemolysis, the levels of the indirect markers are already altered as a result of concomitant disease. As a result, patient care is adversely affected because his or her therapy might be initiated or changed based upon misdiagnosis. Accordingly, there exists a need for an accurate and specific means for diagnosing hemolysis.
Adenylate kinases are a large family of enzymes found in plants, bacteria, and animals. The different members of the adenylate kinase family differ in composition, thermostability, optimum pH, substrate specificities, and kinetics. In humans, a variety of adenylate kinase isoenzymes, from a number of distinct sources, such as liver, intestine, muscle and erythrocytes, can be found in serum.
The inventors of the present invention have discovered that the level of erythrocyte adenylate kinase in serum correlates with the degree of hemolysis of blood. Based upon this discovery, the inventors of the present invention have devised an accurate method for detecting hemolysis in blood. Accordingly, the present invention satisfies the need for an accurate means for diagnosing hemolysis.